Immunophilins are cytosolic proteins that possess peptidyl-prolyl-cis-trans isomerase (PPIase or rotamase) activity. This family of proteins behave as chaperone molecules causing cis-trans isomerization of peptide-prolyl bonds that could be a rate limiting step in the correct folding of certain proteins. They are also involved in many cellular signal transduction pathways as partners in multiprotein complexes for which binding in the rotamase active site, but not rotamase activity per se, appears to be important (Rxc3xchlmann, et al., Immunobiol., 198, pp. 192-206 (1998)). Immunosuppressive drugs such as FK506, rapamycin and cyclosporin A bind to specific groups of immunophilins. FK506 and rapamycin bind to the so-called FK506-binding proteins (FKBPs), whereas the cyclophilins binds to cyclosporin A. It has been shown that binding to the 12 kD immunophilin FKBP12 is necessary for FK506 to elicit its immunosuppressive activity. Subsequently, it was also found that FK506 has two binding domains: one that binds to FKBP12 and the other (the effector domain) for the complex of FK506 and FKBP12 that binds to the serine/threonine phosphatase, calcineurin. This complexation inhibits calcineurin and prevents the proliferation of T-lymphocytes (i.e. immunosuppression). Rapamycin has an effector domain of a different structure, and its complex with FKBP12 binds to a different target protein that, also results in immunosuppression. For a review, see S. L. Schreiber, et al., Tetrahedron, 48, pp. 2545-2558 (1992). Some of the other proteins with which FKBP12 is known to interact include the TGFxcex2 receptor I (Wang, et al., Science , 265, pp. 674-676 (1994)), the IP3 receptor and the ryanodine receptor (Cameron, et al., J. Biol. Chem., 272, pp. 27582-27588 (1997)). In the case of the TGFxcex2 system, it has been suggested that FKBP12 binding inhibits unregulated signalling with consequences for differentiation, apoptosis and proliferation (Wang, et al., Cell, 86, pp. 435-444 (1996)).
While FK506 exhibits immunosuppressive effects, analogs lacking the calcineurin binding effector domain are devoid of immunosuppressive activity. Many small molecules that contain the essential elements of the FKBP12 binding domain of FK506 but lack the calcineurin binding domain were found to retain high affinity binding to FKBP12, and behave as rotamase inhibitors (D. S. Yamshita, et al., Bioorg. Med. Chem. Lett., 4, pp. 325-328 (1994); D. M. Armistead, et al., Acta Cryst. D, 51, pp. 522-528 (1995)).
FK506 has been shown to possess neurotrophic properties in vitro and in vivo (W. E. Lyons, et al., Proc. Natl. Acad. Sci USA, 91, pp. 3191-3195 (1994); B. G. Gold, et al., J. Neurosci., 15, pp. 7509-7516 (1995)). However, its immunosuppressive properties as well as other serious side effects are drawbacks to its use as a neuroregenerative agent. Recently, in vitro studies in PC12 cells, SY5Y cells, and chick sensory dorsal root ganglion explant cultures have shown that small molecule, nonimmunosuppressive FKBP12 rotamase inhibitors also promote neurite outgrowth, and a number of these compounds have shown utility in reversal of CNS lesioning and nerve crush in animal models (G. S. Hamilton, et al., Curr. Pharm. Design, 3, pp. 405-428 (1997); B. G. Gold, et al., Exp. Neurol., 147, pp. 269-278 (1997)). Thus, while the calceineurin binding domain of FK506 is necessary for immunosuppressive activity, it is not required for neurotrophic activity.
A 10-50 fold elevated expression of immunophilins in the central nervous system in comparison with the immune system is well documented (S. H. Snyder, et al., Nature Med., 1, pp. 32-37 (1995)). Recently, augmented expression of FKBP12 m-RNA following facial nerve crush and sciatic nerve lesions was established in facial and lumbar motor neurons. The observed augmentation paralleled the enhanced expression of growth associated protein GAP43 mRNA (B. G. Gold, et al., Neurosci. Lett., 241, pp. 25-28 (1998)). These observations make FKBP12 an attractive target for developing nonimmunosuppressive rotamase inhibitors which promote neurite outgrowth. Such compounds are potential therapeutics to reverse neuronal damage caused by neurodegenerative disease or physical trauma.
Recently, Gold and co-workers (J. Pharm. Exp. Ther., 289, pp. 1202-1210 (1999)) have proposed that neurotrophic FKBP12 binding compounds actually act through binding to the related FK506-binding protein, FKBP52. FKBP52 is known to act as a partner with the chaperone protein hsp90 and p23 in a complex that modulates the activity of steroid receptors. According to this model, compounds such as FK506 that bind to the FKBP52 active site facilitate steroid receptor signaling resulting in neurite growth. Since the FKBP52 rotamase active site is known to be very similar to that of FKBP12 (C. T. Craescu, et al., Biochemistry, 35, pp. 11045-11052 (1996)), it is likely that a large proportion of FKBP12-binding compounds will possess neurotrophic activity if this model is valid.
There have been disclosures of related compounds for overcoming multidrug resistance (MDR) or as immunosuppressants such as:
WO 94/07858 published Apr. 14, 1994
WO 92/19593 published Nov. 12, 1992
U.S. Pat. No. 5,622,970 granted Apr. 22, 1997
U.S. Pat. No. 5,330,993 granted Jul. 19, 1994
U.S. Pat. No. 5,192,773 granted Mar. 9, 1993
U.S. Pat. No. 5,516,797 granted May 14, 1996
WO 92/21313 published Dec. 10, 1992
European Application 564924 published Oct. 13, 1993
European Application 405994 published Jan. 2, 1991
Other prior art disclosing related compounds having neurotrophic activity are:
WO 96/40140 published Dec. 19, 1996
WO 96/40633 published Dec. 19, 1996
WO 97/16190 published May 9, 1997
WO 96/41609 published Dec. 27, 1996
U.S. Pat. No. 5,696,135 granted Dec. 9, 1997
WO 97/36869 published Oct. 9, 1997
U.S. Pat. No. 5,721,256 granted Feb. 24, 1998
U.S. Pat. No. 5,654,332 granted Aug. 5, 1997
WO 98/13343 published Apr. 2, 1998
WO 98/13355 published Apr. 2, 1998
WO 98/20891 published May 22, 1998
WO 98/20892 published May 22, 1998
WO 98/20893 published May 22, 1998
WO 98/29116 published Jul. 9, 1998
WO 98/29117 published Jul. 9, 1998
WO 99/10340 published Mar. 4, 1999
WO 99/21552 published May 6, 1999
U.S. Pat. No. 5,780,484 granted Jul. 14, 1998
U.S. Pat. No. 5,786,378 granted Jul. 28, 1998
U.S. Pat. No. 5,795,908 granted Aug. 18, 1998
U.S. Pat. No. 5,798,355 granted Aug. 25, 1998
U.S. Pat. No. 5,801,187 granted Sep. 1, 1998
U.S. Pat. No. 5,801,197 granted Sep. 1, 1998
Since there are relatively few FKBP12-binding compounds that are known to stimulate neurite growth, there remains a great need for additional neurotrophic, FKBP12-binding compounds.
Surprisingly, applicant has solved the aforementioned problem. The present invention relates to novel bicyclic diamide compounds and pharmaceutical compositions thereof that possess neurotrophic and/or neuroprotective properties.